Last Winter I rebuilt a 355 that I had built for a friend a few years back and we decided to make some of the changes then run it to see where the power is gained before putting on better heads that I am working on for next year. Went to a 383ci but used the same upper end parts and pistons. I think the knife edging, gas porting and low tension ring pkg was at least half the gain. I think it gained about 50hp from the ET change.Here is a link where some of my decisions related to gas porting and rings were discussed.http://www.motorsportsvillage.com/forum/viewtopic.php?f=5&t=8030

383ci same block but decked enough to make up for piston/rod difference (~.015")3.75" LJ crank that I knife edged counterweights.5.85"rodsSame pistons but drilled vertical gas ports and used low tension ringsI did some profiling of the dome but CR would go up ~1 point to ~14:1All other parts stayed the same.

This Malibu started out running 7.30's with a lot of the same parts. Over the years there have been a lot of things "tweaked" as needed. The heads and intake got a lot of work, much of which doesn't show in the flowbench numbers.

It had a 1.320 60' and the wheels in the air. We aren't sure what will happen with the other heads I'm working on. Flowed a port last night. 310cfm and 215cc's but still have a little too much velocity at the pushrod expansion.

Rick, we had talked about the bigger inch engine not wanting shifted at a lower rpm when the same top end was used.

rick360 wrote:

I think the knife edging, gas porting and low tension ring pkg was at least half the gain.

I think this is atleast part of the reason. I hadn't put it together that Tommy's 355 didn't have those things until reading it here. (or my brain just got around to processing the info)Knife edged crank, low tension rings would help pumping losses to not go up as quick and would help power to hang on after peak power. The compression increase could help that a little also.

That 6.18 should be about a 9.60 1/4 mile. I think he should have run it out the 1/4 mile. The 5700 fpm mean piston speed shouldn't be a problem, should it??